1. Field of the Invention
The present invention relates generally to implantable medical devices, and more specifically, relates to implantable medical devices for the treatment of male impotence.
2. Description of the Prior Art
Implantable cylinders for the treatment of male impotence have been in use for some time. The more sophisticated of these devices employ fluid systems whereby the cylinder may be evacuated to produce the flaccid state and inflated to produce the erect state.
An early patent disclosing such an implantable system is U.S. Pat. No. 4,009,711, issued to Uson et al., which uses a pair of inflatable cylinders implanted in a corpus cavernosum of the penis. Each of the cylinders include a non-distensible portion of a semi-rigid material to be implanted into the root end of the corpus cavernosum and a pendulous, distensible body portion. The distensible body portion or inflatable cylinder is connected by tubing to a fluid reservoir located in the scrotal sac, and a check valve is provided to control the flow of fluid between the reservoir and the inflatable cylinder. A similar device is disclosed in U.S. Pat. No. 4,235,227, issued to Yamanaka.
A more recent design of a prosthesis is found in U.S. Pat. No. 4,726,360 which discloses that each inflatable tube can be encased in an outer sleeve which is permanently filled with a fluid, thereby providing an outer, annular pressure chamber. The distensible cylinders described in these references are formed of silicone rubber and have limited elasticity to avoid girth expansion of the cylinders upon inflation. This limited elasticity of the cylinders, however, undesirably limits the longitudinal growth from flaccid state to erect state.
U.S. Pat. No. 4,730,607, issued to Fischell suggests that the longitudinal growth of a stiffener cylinder can be improved by providing several bellow-type folds in the cylinder. The bellow-type folds are described as having sufficient depth to increase the extendibility of the cylinder from 6 percent to about 13 percent. Fischell teaches that these folds should be located near the base to function as a strain relief in the flaccid state.
Even though the Fischell device is a minimal attempt at providing an extendible stiffening cylinder, the total length increase in the prior art devices is very small compared to that which occurs under normal conditions from flaccid to erect state.